On Thu, Nov 15, 2018 at 04:52:56PM +0800, Ming Lei wrote:
> There are still cases in which we need to use bio_bvecs() for get the
> number of multi-page segment, so introduce it.

The only user in your final tree seems to be the loop driver, and
even that one only uses the helper for read/write bios.

I think something like this would be much simpler in the end:

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index d509902a8046..712511815ac6 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -514,16 +514,18 @@ static int lo_rw_aio(struct loop_device *lo, struct 
loop_cmd *cmd,
        struct request *rq = blk_mq_rq_from_pdu(cmd);
        struct bio *bio = rq->bio;
        struct file *file = lo->lo_backing_file;
+       struct bvec_iter bvec_iter;
+       struct bio_vec tmp;
        unsigned int offset;
        int nr_bvec = 0;
        int ret;
 
+       __rq_for_each_bio(bio, rq)
+               bio_for_each_bvec(tmp, bio, bvec_iter)
+                       nr_bvec++;
+
        if (rq->bio != rq->biotail) {
-               struct bvec_iter iter;
-               struct bio_vec tmp;
 
-               __rq_for_each_bio(bio, rq)
-                       nr_bvec += bio_bvecs(bio);
                bvec = kmalloc_array(nr_bvec, sizeof(struct bio_vec),
                                     GFP_NOIO);
                if (!bvec)
@@ -537,7 +539,7 @@ static int lo_rw_aio(struct loop_device *lo, struct 
loop_cmd *cmd,
                 * API will take care of all details for us.
                 */
                __rq_for_each_bio(bio, rq)
-                       bio_for_each_bvec(tmp, bio, iter) {
+                       bio_for_each_bvec(tmp, bio, bvec_iter) {
                                *bvec = tmp;
                                bvec++;
                        }
@@ -551,7 +553,6 @@ static int lo_rw_aio(struct loop_device *lo, struct 
loop_cmd *cmd,
                 */
                offset = bio->bi_iter.bi_bvec_done;
                bvec = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
-               nr_bvec = bio_bvecs(bio);
        }
        atomic_set(&cmd->ref, 2);
 
diff --git a/include/linux/bio.h b/include/linux/bio.h
index dcad0b69f57a..379440d1ced0 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -200,30 +200,6 @@ static inline unsigned bio_segments(struct bio *bio)
        }
 }
 
-static inline unsigned bio_bvecs(struct bio *bio)
-{
-       unsigned bvecs = 0;
-       struct bio_vec bv;
-       struct bvec_iter iter;
-
-       /*
-        * We special case discard/write same/write zeroes, because they
-        * interpret bi_size differently:
-        */
-       switch (bio_op(bio)) {
-       case REQ_OP_DISCARD:
-       case REQ_OP_SECURE_ERASE:
-       case REQ_OP_WRITE_ZEROES:
-               return 0;
-       case REQ_OP_WRITE_SAME:
-               return 1;
-       default:
-               bio_for_each_bvec(bv, bio, iter)
-                       bvecs++;
-               return bvecs;
-       }
-}
-
 /*
  * get a reference to a bio, so it won't disappear. the intended use is
  * something like:

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